1. No category

doi number
Communication
J. Braz. Chem. Soc., Vol. 00, No. 00, 1-9, 2015.
Printed in Brazil - ©2015 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Synthesis of 4-Arylselanylpyrazoles Through Cyclocondensation Reaction Using
Glycerol as Solvent
José E. R. Nascimento, Daniela H. de Oliveira, Paola B. Abib, Diego Alves, Gelson Perin
and Raquel G. Jacob*
Laboratório de Síntese Orgânica Limpa (LASOL), Centro de Ciências Químicas,
Farmacêuticas e de Alimentos (CCQFA), Universidade Federal de Pelotas (UFPel),
P.O. Box 354, 96010-900 Pelotas-RS, Brazil
We describe here a simple method to synthesize 4-arylselanylpyrazoles by reaction of
α-arylselanyl-1,3-diketones with arylhydrazines using glycerol as solvent at 60 °C under N2
atmosphere. This is a direct cyclocondensation reaction performed with α-arylselanyl-1,3-diketones
and arylhydrazines bearing electron-withdrawing and electron-donating groups affording the
corresponding 4-arylselanylpyrazoles in moderate to good yields.
Keywords: green chemistry, glycerol, pyrazole, heterocycle, organoselenium compound
Introduction
Pyrazoles represent a significant class of heterocyclic
compounds used widely in agrochemical and especially
pharmaceutical industry. 1 This class of biologically
active nitrogen compounds exhibit a number of important
pharmacology properties, such as antibacterial, antiobesity,
antitumor, antileukemic, anti-inflammatory and analgesic.2
For example, substituted pyrazoles constitute the core
structures of important commercial drugs, such as
Celecoxib, 3 Metamizole, 4 Zaleplon, 5 Sildenafil 6 and
Fipronil7 (Figure 1).
The synthesis of these heterocyclic compounds can be
achieved by several different methods. Generally pyrazoles
could be synthesized by reaction of 1,3-dicarbonyl
compounds with hydrazines,8 1,3-dipolar cycloadition
employing alkenes or alkynes,9 reaction of unsaturated
aldehydes or ketones with hydrazines,10 the functionalization
of unsubstituted pyrazoles,11 among others.12 Therefore, the
search for a practical reaction system for the synthesis of
substituted pyrazoles in terms of mild reaction conditions
and economic viability, continues to attract the interest of
synthetic organic chemists.
In this sense, the development of methodologies
employing recyclable and environmentally friendly
solvents has gained much interest recently, because of
the extensive use of solvents in almost all of the chemical
*e-mail: raquel.jacob@ufpel.edu.br
and pharmaceutical industries, and of the predicted
disappearance of fossil oil.13 With the increase in biodiesel
production and consequently, the market saturation of
glycerol, in the last years, this side product of biodiesel
production emerged as an alternative for the replacement
of conventional solvents.14
The use of glycerol as a sustainable solvent for green
chemistry was recently reported,14 particularly for the
synthesis of organoselenium compounds.15 Organoselenium
compounds are attractive molecules due to their selective
reactions16 and are often linked to interesting biological
activities.17 Among organoselenium compounds, those
containing nitrogen heterocycles in their structure are of
special interest and this class of molecules has shown a
range of pharmacological properties.17,18 However, there
are few reports on the preparation of selanyl-substituted
pyrazoles and as example, bis(3R,5R’-1H-pyrazol-4-yl)
selenides were synthesized in high yields by reaction
between 3- and 3,5-substituted pyrazoles with selenium
dioxide.19 Consequently, the search for new and efficient
methods for the synthesis of nitrogen-functionalized
organoselenium compounds, more specifically selanylsubstituted pyrazoles, remains a challenge in organic
chemistry.
In view of the explained above, we report here our
contribution to the application of glycerol as solvent
in the synthesis of selanyl-substituted heterocycles.
The present methodology describes a simple method to
synthesize a range of 4-arylselanylpyrazoles by reaction
2
Synthesis of 4-Arylselanylpyrazoles Through Cyclocondensation Reaction Using Glycerol as Solvent
CF 3
NC
SO 3H
N
N
N
N
N
O
N
J. Braz. Chem. Soc.
N
N
N Et
SO2 NH 2
O
Celecoxib
O
EtO
Zaleplon
Metamizole
N
N
nPr
N
N
H
O
F3 C S
CN
N
N
H2 N
Cl
Cl
O 2S N
CF3
N
Sildenafil
Fipronil
Figure 1. Drugs containing pyrazole moiety in their structure.
O
O
R1
R2
+
Se
1a- f
R3
R4
NH
NH 2
2a -f
Glycerol
60 °C, N 2
N
R1
N
R4
R2
R3
Se
3a -k
Scheme 1. General scheme of the reaction.
of α-arylselanyl-1,3-diketones with arylhydrazines using
glycerol as solvent (Scheme 1).
Results and Discussion
Initially, we chose α-phenylselanylacetylacetone 1a
and phenylhydrazine 2a as model substrates to establish
the best conditions for this reaction and some experiments,
including solvent tests, stoichiometry and temperature
were performed to synthesize 3,5-dimethyl-1-phenyl-4(phenylselanyl)-1H-pyrazole 3a (Table 1). The starting
material 1a, which exists predominantly in enolic form
(ratio of keto:enol = 1:9), was synthesized according
protocol described by Sonoda and co-workers.20
Thus, a mixture of α-phenylselanylacetylacetone
1a (0.5 mmol) and phenylhydrazine 2a (0.5 mmol) in
glycerol (1.0 mL) was stirred at room temperature under
air atmosphere for 5 h. Under these reaction conditions,
the product 3a was obtained only in 35% yield and a
slight decomposition of the starting material during the
reaction time was observed (Table 1, entry 1). Aiming to
improve the yield of product 3a a mixture of compound 1a
and phenylhydrazine 2a in glycerol was reacted in open
atmosphere at 60 and 90 °C. Interestingly, when we
carried out the reaction at 60 °C, the desired product 3a
was obtained in 70% yield after 4 h (Table 1, entry 2).
However, when the temperature of reaction was increased
to 90 °C, the desired product 3a was formed in 55% and a
great decomposition of starting material 1a was observed
after 1.5 h (Table 1, entry 3). An increase in the yield was
obtained when the reaction was performed at 60 °C under
N2 atmosphere (Table 1, entry 4). Unfortunately, when
the reaction was carried out at room temperature under
N2 atmosphere, it yielded the product 3a in 40% (Table 1,
entry 5). Gratefully, when the reaction was performed
at 60 °C under N2 atmosphere using a little excess of
Vol. 00, No. 00, 2015
3
Nascimento et al.
Table 1. Reaction conditions optimizationa
O
O
+
NH
NH 2
Conditions
N
N
Se
Se
2a
3a
1a
1a / mmol
Solvent
Temperature / °C
timeb / h
Yieldc / %
1
0.5
Glycerol
r.t.
5.0
35
2
0.5
Glycerol
60
4.0
70
3
0.5
Glycerol
90
1.5
55
4
0.5
Glycerol
60
3.0
75d
5
0.5
Glycerol
r.t.
5.5
40d
6
0.6
Glycerol
60
3.0
82d
7
0.6
PEG-400
60
5.0
27d
8
0.6
H2O
60
5.0
53d
9
0.6
EtOH
60
5.0
77d
10
0.6
–
60
5.0
45d
entry
Reactions were performed using α-phenylselanylacetylacetone 1a, phenylhydrazine 2a (0.5 mmol) and 1.0 mL of solvent; bduring this time, a slight
decomposition of the starting material 1a in diphenyl diselenide and 2,4-pentanedione was observed. Traces of 3,5-dimethyl-1-phenyl-1H-pyrazole were
observed as by-product; cyields are given for isolated product 3a; dreactions were performed under N2 atmosphere. PEG: polyethylene glycol; r.t.: room
temperature.
a
substrate 1a (0.6 mmol), the corresponding product
3a was obtained in 82% after 3.0 h (Table 1, entry 6).
Regarding the influence of the solvent on the reaction,
a range of environmentally friendly solvents were tested
on the same protocol described above and the desired
product 3a was obtained in lower yields compared with
the reaction performed in glycerol (Table 1, entries 6 vs.
7-9). Finally, the reaction was performed without solvent at
60 °C and product 3a was obtained in 45% yield (Table 1,
entry 10). In this reaction without solvent we observed the
decomposition of the starting material 1a after 5 h at 60 °C.
In fact, and according to our observations, during the
whole time in all reactions the starting material 1a suffers
decomposition. This result is not surprising since this starting
material can undergo a C–Se bond cleavage prompted
by temperature or exposure to light.21 The formation of
3,5-dimethyl-1-phenyl-1H-pyrazole as by-product could
be explained by the cyclocondensation of 2,4-pentanedione
with phenylhydrazine 2a in the reaction media.
In an optimized reaction, α-phenylselanylacetylacetone
1a (0.6 mmol) and phenylhydrazine 2a (0.5 mmol) were
dissolved in glycerol (1.0 mL). The reaction mixture
was stirred for 3 h at 60 °C under nitrogen atmosphere,
affording 3,5-dimethyl-1-phenyl-4-(phenylselanyl)-1Hpyrazole 3a in 82% yield. It is important to mention that
this cyclocondensation occurs without the presence of
any catalyst. This result is in agreement with previous
reports in literature in which electrophilic activation of
carbonyl compounds in glycerol-promoted reactions allows
eliminating the use of acidic catalysts.22
In order to demonstrate the efficiency of this reaction,
we explored the generality of our method extending the
conditions to other differently substituted α-arylselanyl1,3-diketones 1a-f and different arylhydrazines 2a-f, and the
results are summarized in Table 2. The results disclosed in
Table 2 reveal that the reaction worked well with a range of
substituted arylhydrazines 2 containing electron-donating
groups (EDG) and electron-withdrawing groups (EWG)
at the aromatic ring, affording moderate to good yields of
the desired 4-arylselanylpyrazoles 3. Our results reveal that
the reactions are not sensitive to the electronic effect of the
aromatic ring in the arylhydrazine. Therefore, a comparison
between entries 1-5 vs. 6, in which arylhydrazines with
EDG and EWG were used, displays similar yields for the
obtained products (Table 2, entries 1-6).
In addition, the possibility of performing the
reaction with other α-arylselanyl-1,3-diketones 1b-f was
investigated. These α-arylselanyl-1,3-diketones 1b-f were
also synthesized according to Sonoda and co-workers.20
Phenylhydrazine 2a was efficiently cyclocondensed with
a range of α-arylselanyl-1,3-diketones, affording the
respective 4-arylselanylpyrazoles 3 in acceptable yields
4
Synthesis of 4-Arylselanylpyrazoles Through Cyclocondensation Reaction Using Glycerol as Solvent
J. Braz. Chem. Soc.
Table 2. Generality in the synthesis of 4-arylselanylpyrazolesa
O
R
O
1
2
R
+
R4
Se
1a-f
entry
R1
N
R3
N
R4
Se
R2
3a-k
Arylhydrazine
timeb / h
Product
Yieldc / %
O
H
N
1
Glycerol
60 °C, N 2
2a-f
R3
α-Arylselanyl-1,3diketone
O
NH
NH 2
Se
N
NH2
N
3.0
82
Se
2a
3a
1a
H
N
1a
2
N
NH2
N
4.0
2b
3b
H
N
N
NH2
1a
3
79
Se
N
4.5
81
Se
3c
2c
H
N
1a
4
N
NH2
N
3.0
2d
3d
H
N
1a
5
N
NH2
O
3.5
N
2e
3e
H
N
1a
6
N
NH2
F
N
3.5
2f
73
Se
F
F
O
77
Se
O
F
84
Se
3f
O
N
7
2a
Se
N
2.5
87
Se
3g
1b
O
O
N
N
8
Se
2a
Se
5.0
N
76d
N
Se
1c
3h
3h’
Vol. 00, No. 00, 2015
5
Nascimento et al.
Table 2. Generality in the synthesis of 4-arylselanylpyrazolesa (cont.)
entry
α-Arylselanyl-1,3diketone
O
Arylhydrazine
timeb / h
Product
O
N
Se
9
Yieldc / %
2a
3.0
68
Se
O
3i
1d
O
O
N
O
N
10
2a
Se
3.0
N
79
Se
3j
1e
O
O
N
11
Se
2a
3.0
Cl
N
Se
72
3k
Cl
1f
Reactions were performed using α-arylselanyl-1,3-diketones 1a-f (0.6 mmol), arylhydrazines 2a-f (0.5 mmol) in glycerol (1.0 mL) at 60 °C under
N2 atmosphere; bduring this time, a slight decomposition of starting materials 1a-f in diaryl diselenides and 1,3-diketones was observed. Traces of
3,5-disubstituted 1-aryl-1H-pyrazoles without arylselenium moiety were observed as by-product; cyields are given for isolated 4-arylselanylpyrazoles; da
mixture of regioisomers in a ratio 3h/3h’ (96:4) were obtained and determined by 1H NMR.
a
(Table 2, entries 7-11). α-Arylselanyl-1,3-diketones 1b
and 1c furnished the corresponding selanylpyrazoles 3g
and 3h in 87 and 76% yield, respectively (Table 2, entries 7
and 8). In the reaction carried out with the unsymmetrical
substrate 1c, the formation of traces of regioisomer 3h’ was
observed (Table 2, entry 8). We believe that the conjugative
effect of aromatic ring in substrate 1c, that stabilizes the
enol-tautomer, can selectively contribute to increase the
regioselectivity of this cyclization towards the formation
of product 3h. Besides, α-arylselanyl-1,3-diketones 1d-f
derived from substituted diaryl diselenides containing
substituents such as OMe, Me and Cl furnished good yields
of desired selanylpyrazoles 3i-k (Table 2, entries 9-11).
Conclusions
In summary, we developed a simple method to
synthesize a range of 4-arylselanylpyrazoles by reaction
of α-arylselanyl-1,3-diketones with arylhydrazines using
glycerol as solvent. Cyclocondensations of α-arylselanyl1,3-diketones with arylhydrazines were performed using
glycerol as solvent at 60 °C under N2 atmosphere and
establishing a route to obtain 4-arylselanylpyrazoles
containing electron-withdrawing and electron-donating
groups in moderate to good yields. The toxicological
and pharmacological evaluations of the synthesized
arylselanylpyrazoles are under study in our laboratories.
Experimental
General remarks
The reactions were monitored by thin-layer
chromatography (TLC) carried out on Merck silica gel
(60 F254) by using UV light as visualizing agent and 5%
vanillin in 10% H2SO4 and heat as developing agents.
Baker silica gel (particle size 0.040-0.063 mm) was
used for flash chromatography. Proton nuclear magnetic
resonance (1H NMR) spectra were obtained at 300 MHz
on a Varian Gemini NMR and at 400 MHz on Bruker
DPX 400 spectrometers. Spectra were recorded in CDCl3
solutions. Chemical shifts are reported in ppm, referenced
to tetramethylsilane (TMS) as the external reference.
Coupling constants (J) are reported in Hertz. Carbon-13
nuclear magnetic resonance (13C NMR) spectra were
obtained at 75 MHz on a Varian Gemini NMR and at
100 MHz on Bruker DPX 400 spectrometers. Chemical
shifts are reported in ppm, referenced to the solvent peak
of CDCl3. Low-resolution mass spectra (MS) were obtained
with a Shimadzu GC-MS-QP2010 mass spectrometer.
6
Synthesis of 4-Arylselanylpyrazoles Through Cyclocondensation Reaction Using Glycerol as Solvent
Glycerol 99.5% was purchased from Synth® (Brazil) and
was used without previous purification.
General procedure for the synthesis of 4-arylselanylpyrazoles
To a 5 mL round-bottomed flask containing an
appropriate α-arylselanyl-1,3-diketone 1a-f (0.6 mmol)
and arylhydrazine 2a-f (0.5 mmol) was added 1.0 mL of
glycerol. The resulting solution was stirred 60 °C at N2
atmosphere for the time indicated in Table 2. After that, the
reaction mixture was received in water (20.0 mL), extracted
with ethyl acetate (3 × 5.0 mL), dried over MgSO4, and
concentrated under vacuum. The residue was purified by
column chromatography on silica gel using ethyl acetate/
hexane as the eluent.
3,5-Dimethyl-1-phenyl-4-(phenylselanyl)-1H-pyrazole (3a)
Yield 82%; orange solid;
m.p. 67-69 °C; 1 H NMR
Se
(300 MHz, CDCl3) d 7.44‑7.46
(m, 4H), 7.32-7.39 (m, 1H),
7.17-7.19 (m, 4H), 7.10-7.14 (m, 1H), 2.36 (s, 3H), 2.33 (s,
3H); 13C NMR (75 MHz, CDCl3) d 153.05, 143.87, 139.66,
132.79, 128.98, 128.95, 128.12, 127.56, 125.58, 124.54,
102.42, 12.82, 12.32; MS (relative intensity) 330 (2), 329
(12), 328 (M+, 12), 327 (65), 326 (8), 325 (35), 324 (13),
248 (23), 247 (29), 246 (100), 231 (7), 206 (5), 171 (3),
130 (8), 118 (34), 115 (3), 103 (5), 91 (4), 78 (9), 77 (90),
65 (5), 51 (24), 41 (3).
N
N
3,5-Dimethyl-4-(phenylselanyl)-1-o-tolyl-1H-pyrazole (3b)
Yield 79%; yellow oil;
H NMR (300 MHz, CDCl3)
Se
d 7.33-7.37 (m, 2H), 7.25-7.30
(m, 2H), 7.11-7.20 (m, 5H),
2.33 (s, 3H), 2.12 (s, 3H), 2.08 (s, 3H); 13C NMR (75 MHz,
CDCl3) d 152.82, 145.06, 138.65, 135.91, 133.20, 130.90,
129.28, 129.06, 127.94, 127.61, 126.58, 125.56, 100.47,
17.15, 12.91, 11.26; MS (relative intensity) 344 (12), 343
(9), 342 (M+, 67), 341 (9), 340 (33), 339 (13), 338 (12), 325
(2), 281 (3), 262 (85), 261 (91), 246 (30), 232 (9), 221 (11),
220 (17), 207 (4), 204 (8), 185 (5), 178 (3), 169 (7), 157
(6), 144 (13), 132 (49), 128 (5), 115 (14), 106 (4), 103 (6),
92 (9), 91 (100), 89 (12), 77 (29), 65 (53), 51 (19), 41 (4).
N
1
N
1-(2,5-Dimethylphenyl)-3,5-dimethyl-4-(phenylselanyl)-1Hpyrazole (3c)
N
Yield 81%; yellow oil;
H NMR (300 MHz, CDCl3)
d 7.13-7.25 (m, 8H), 2.37 (s,
3H), 2.32 (s, 3H), 2.11 (s, 3H),
1
N
Se
J. Braz. Chem. Soc.
2.03 (s, 3H); 13C NMR (75 MHz, CDCl3) d 152.70, 145.14,
139.18, 136.14, 135.48, 133.29, 131.49, 129.05, 127.89,
127.34, 127.18, 125.52, 100.25, 21.13, 17.07, 12.92, 11.26;
MS (relative intensity) 358 (19), 357 (21), 356 (M+, 100),
355 (15), 354 (50), 352 (20), 341 (9), 339 (4), 276 (29),
275 (62), 261 (58), 260 (25), 246 (8), 234 (12), 222 (17),
220 (10), 198 (8), 184 (30), 169 (7), 159 (22), 157 (15),
146 (20), 131 (16), 115 (17), 105 (28), 103 (26), 91 (31),
79 (38), 77 (64), 65 (15), 51 (14), 41 (4).
3,5-Dimethyl-4-(phenylselanyl)-1-m-tolyl-1H-pyrazole (3d)
Yield 84%; yellow oil;
H NMR (300 MHz, CDCl3)
Se
d 7.32-7.37 (m, 2H), 7.19-7.25
(m, 7H), 2.41 (s, 3H), 2.37 (s,
3H), 2.33 (s, 3H); 13C NMR (75 MHz, CDCl3) d 153.06,
143.99, 139.68, 139.25, 132.94, 129.07, 128.74, 128.50,
128.21, 125.66, 125.45, 121.65, 102.29, 21.29, 12.89,
12.40; MS (relative intensity) 344 (15), 343 (2), 342 (M+,
67), 340 (34), 338 (13), 263 (16), 261 (100), 246 (31), 244
(13), 232 (10), 221 (11), 220 (16), 205 (5), 169 (5), 157
(5), 143 (8), 132 (33), 130 (11), 117 (4), 115 (10), 91 (74),
77 (22), 65 (37), 51 (14), 41 (3).
N
1
N
1-(4-Methoxyphenyl)-3,5-dimethyl-4-(phenylselanyl)-1Hpyrazole (3e)
N
Yield 77%; yellow
oil; 1H NMR (300 MHz,
CDCl 3) d 7.36 (d, 2H,
J 9.02 Hz), 7.11-7.19 (m, 5H), 6.97 (d, 2H, J 9.02 Hz),
3.84 (s, 3H), 2.32 (s, 6H); 13C NMR (75 MHz, CDCl3)
d 159.00, 152.79, 144.10, 132.99, 132.89, 129.04, 128.19,
126.24, 125.62, 114.14, 101.75, 55.45, 12.85, 12.16;
MS (relative intensity) 358, (38), 278 (100), 148 (33),
77 (32).
O
N
Se
1-(2,4-Difluorophenyl)-3,5-dimethyl-4-(phenylselanyl)-1Hpyrazole (3f)
Yield 73%; yellow
oil; 1H NMR (300 MHz,
Se
CDCl 3) d 7.46-7.50 (m,
F
1H), 7.15-7.26 (m, 5H),
7.00-7.04 (m, 2H), 2.31 (s, 3H), 2.23 (d, 3H, J 1.8 Hz);
13
C NMR (75 MHz, CDCl3) d 162.54 (dd, J 250.49,
11.05 Hz), 156.95 (dd, J 252.91, 12.53 Hz), 154.09, 146.23,
132.67, 129.92 (dd, J 10.02, 1.35 Hz), 129.13, 128.22,
125.76, 124.02 (dd, J 12.37, 4.05 Hz), 112.01 (dd, J 22.34,
3.89 Hz), 104.93 (dd, J 26.29, 23.61 Hz), 101.97, 12.93,
11.25 (d, J 3.64 Hz); MS (relative intensity) 366 (12), 365
(6), 364 (M+, 59), 362 (30), 284 (99), 283 (63), 269 (7),
268 (18), 263 (9), 256 (8), 243 (11), 242 (16), 236 (4), 222
N
F
N
Vol. 00, No. 00, 2015
(5), 207 (8), 194 (2), 166 (6), 155 (13), 154 (100), 143 (5),
140 (7), 128 (16), 127 (28), 113 (42), 103 (9), 91 (6), 77
(32), 65 (11), 63 (3), 41 (6).
3,5-Diethyl-1-phenyl-4-(phenylselanyl)-1H-pyrazole (3g)
Yield 87%; orange oil;
H NMR (400 MHz, CDCl3)
N
N
d 7.44-7.48 (m, 4H), 7.35-7.40
Se
(m, 1H), 7.15-7.21 (m, 4H),
7.10-7.13 (m, 1H), 2.78 (q, 2H,
J 7.53, 7.55 Hz), 2.72 (q, 2H, J 7.57, 7.55 Hz), 1.23 (t, 3H,
J 7.57 Hz), 0.99 (t, 3H, J 7.56 Hz); 13C NMR (100 MHz,
CDCl3) d 158.24, 149.68, 140.10, 133.63, 129.08, 128.98,
128.12, 127.99, 125.56, 125.35, 100.41, 20.84, 19.15,
13.82, 13.62; MS (relative intensity) 358 (7) 357 (8), 356
(M+, 7), 355 (30), 353 (16), 326 (1), 276 (24), 275 (100),
260 (6), 246 (5), 231 (6), 217 (1), 204 (3), 197 (6), 183 (4),
169 (3), 155 (2), 143 (4), 132 (16), 128 (2), 117 (5), 104
(6), 91 (8), 77 (46), 65 (3), 51 (9), 41 (2).
1
5-Methyl-1,3-diphenyl-4-(phenylselanyl)-1H-pyrazole (3h)
Yield 76%; yellow oil;
H NMR (300 MHz, CDCl3)
Se
d 7.24-7.28 (m, 8H), 7.14‑7.20
(m, 7H), 2.39 (s, 3H);
13
C NMR (75 MHz, CDCl3)
d 153.94, 147.00, 139.85,
133.22, 130.09, 129.90, 129.10, 128.73, 128.63, 128.49,
128.13, 127.16, 125.76, 124.76, 103.42, 13.00; MS
(relative intensity) 392 (10), 391 (7), 390 (M+, 15), 389
(58), 387 (30), 311 (22), 310 (100), 309 (99), 293 (5),
280 (7), 270 (7), 268 (12), 241 (1), 232 (9), 218 (8), 205
(6), 190 (6), 180 (21), 178 (7), 165 (16), 152 (3), 130 (5),
127 (7), 118 (4), 102 (7), 91 (6), 89 (15), 77 (93), 51 (30),
41 (2).
N
1
N
7
Nascimento et al.
3,5-Dimethyl-1-phenyl-4-(p-tolylselanyl)-1H-pyrazole (3j)
Yi e l d 7 9 % ; y e l l ow
solid; m.p. 85-86 °C;
1
Se
H NMR (300 MHz, CDCl3)
d 7.46‑7.48 (m, 4H), 7.35-7.40 (m, 1H), 7.10-7.13 (m, 2H),
7.01-7.04 (m, 2H), 2.38 (s, 3H), 2.33 (s, 3H), 2.28 (s, 3H);
13
C NMR (75 MHz, CDCl3) d 153.16, 143.88, 139.87,
135.67, 129.92, 129.08, 128.99, 128.74, 127.69, 124.74,
103.00, 20.91, 12.95, 12.46; MS (relative intensity) 344
(12), 343 (6), 342 (M+, 39), 340 (22), 339 (8), 262 (100),
261 (53), 246 (19), 244 (7), 232 (7), 220 (13), 204 (5), 171
(7), 169 (5), 156 (2), 144 (8), 130 (11), 118 (46), 115 (6),
103 (7), 91 (19), 89 (7), 77 (86), 63 (6), 51 (19), 41 (4).
N
N
4-(4-Chlorophenylselanyl)-3,5-dimethyl-1-phenyl-1Hpyrazole (3k)
Yi e l d 7 2 % ; w h i t e
solid; m.p. 88-89 °C;
1
Se
H NMR (300 MHz,
CDCl 3) d 7.46‑7.48 (m,
4H), 7.38‑7.41 (m, 1H), 7.10-7.19 (m, 4H), 2.37 (s, 3H),
2.32 (s, 3H); 13C NMR (75 MHz, CDCl3) d 153.07, 144.02,
139.71, 131.75, 131.20, 129.58, 129.18, 129.11, 127.82,
124.70, 102.31, 12.87, 12.38; MS (relative intensity) 364
(11), 363 (4), 362 (M+, 17), 361 (81), 359 (42), 346 (2),
284 (31), 282 (100), 281 (73), 266 (12), 264 (6), 251 (5),
246 (37), 240 (10), 230 (4), 219 (3), 205 (10), 204 (9), 190
(2), 171 (4), 164 (5), 154 (4), 130 (9), 123 (4), 118 (56),
115 (5), 104 (4), 91 (3), 77 (91), 65 (6), 51 (20), 41 (4).
N
N
Cl
Supplementary Information
Supplementary data are available free of charge at http://
jbcs.sbq.org.br as PDF file.
Acknowledgments
4-(Methoxyphenylselanyl)-3,5-dimethyl-1-phenyl-1Hpyrazole (3i)
Yield 68%; red oil;
H
NMR (300 MHz,
N
CDCl
3 ) d 7.38-7.46 (m,
Se
4H), 7.33-7.37 (m, 1H),
7.20 (d, 2H, J 8.89 Hz), 6.77 (d, 2H, J 8.88 Hz), 3.75 (s,
3H), 2.39 (s, 3H), 2.34 (s, 3H); 13C NMR (75 MHz, CDCl3)
d 158.41, 152.87, 143.54, 139.81, 131.02, 129.02, 127.61,
124.67, 122.60, 114.84, 103.82, 55.21, 12.95, 12.44; MS
(relative intensity) 360 (8), 359 (2), 358 (M+, 23), 356 (11),
354 (4), 280 (2), 279 (20), 278 (100), 277 (12), 264 (7), 263
(38), 247 (2), 235 (2), 222 (4), 194 (1), 186 (1), 179 (1),
160 (1), 139 (5), 130 (3), 118 (20), 91 (2), 77 (34), 63 (3),
51 (7), 41 (3).
N
O
We are grateful to FINEP, CAPES, CNPq and
FAPERGS for the financial support.
1
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FAPERGS has sponsored the publication of this article.